The present invention relates to a fabric forming process, and more particularly, to a process of imposing twist on yarn immediately upstream of a fabric forming device to introduce variations in the fabric being manufactured.
It has been conventional in the manufacture of fabrics to utilize yarns which, prior to insertion into the fabric, have either been subjected to some degree of real twist or otherwise bonded together to assure that the individual yarns can withstand the manufacturing process. However, one of the drawbacks involved in such prior art processes has resulted from the use of a binder with which the yarn strands are impregnated. However, as noted in U.S. Pat. No. 3,099,907, the use of a binder in the yarns reduces the field of application of the yarn since the surface characteristics are affected, thus restricting the application of the yarns and fabrics where the feel of the fabric is an important consideration in terms of its marketability. Moreover, the use of a binder often requires its subsequent removal in the process which can materially increase the cost of manufacture of the fabric.
While one method of eliminating the necessity of using a binder is suggested in U.S. Pat. No. 3,099,907, mentioned above, which involves the use of a false twist device immediately upstream of the fabric forming machine, the use of such devices is cumbersome and expensive both in terms of power consumption and maintenance, on the one hand, and on the other, unacceptable downtime is required when any change is desired in the twist that is to be imposed in the yarns being fed to the fabric-forming machine.
The present invention has for its object the provision of a fabric-forming where alternating real twist can be inserted in the yarn being fed to the fabric-forming device so that a variety of interesting fabric effects can be achieved at a very low cost both in terms of installation and maintenance of the device. Also, a particular advantage of the present invention is that the twist insertion device requires little or no power to operate, unlike the false twisting devices such as the rotating spindles, friction discs, or the like in prior art false twist arrangements.
In some prior art arrangements, cylindrical pins have been used to insert twist in a moving yarn strand. While these devices have been successful, particularly in the false twist texturing of synthetic thermoplastic filaments, they have all essentially operated on the basis that the pin is set at a fixed angle with respect to the yarn path, which angle is not varied during the operation.
The present invention takes advantage of the unique properties of a cylindrical pin and its interaction with a yarn where the yarn is wrapped about the pin and translated relative thereto as it has been found that the amount of twist that builds up and which slips past the pin is sensitive to the angle of intersection and particularly to variations in the angle which may be momentarily or continually varied so that the yarn twist that builds up will depend on the transient condition of the angle of intersection relative to the yarn path. It has been found, in particular, that the transient nature of the operation results in a sequential flow of finite lengths of alternating twist in the yarn which, when properly handled downstream of the pin, will appear in the resulting fabric as alternating segments that are locked in the fabric as the fabric is being produced. Since yarn twist is known to affect fabric appearance, porosity, surface texture, bending, rigidity, shrinkage and mechanical aesthetics, the provision of varying twist control of yarns being fed into a fabric will offer the manufacturer an important additional controllable parameter for fabric design and construction. Since the means for imposing twist on the yarn in the feed zone of a fabric-making machine, such as the cylindrical pin disclosed in co-pending U.S. patent application of Backer and Hsu, Ser. No. 399,127, filed July 16, 1982, requires no power consumption and a relatively small capital investment to install a very economical process is provided by the present invention which can attain novel fabric characteristics with a relatively modest cost.
In summary, the present invention contemplates providing in the feed zone of a fabric-forming machine which may be a conventional textile loom or knitting machine, a yarn twisting device in the form of a cylindrical pin, one for each yarn strand, about which each yarn strand is wrapped 360.degree. or less and a mechanism for varying, either randomly or continually, the angle of intersection of the pin with the yarn path in a transient manner to allow alternating real twist past the pin during such transient motion of the pin whereby the twist will be inserted and locked into the fabric being formed in the loom or knitting machine. Where a plurality of yarn ends are being employed to form a fabric, the angle of intersection of the cylindrical pins for each of the yarn ends may be varied uniformly or randomly with respect to each other to produce interesting yarn effects in the resulting fabric.
The foregoing and other objects of the present invention will become apparent as consideration is given to the following detailed description taken in conjunction with the accompanying drawings, in which: